Method of making loud-speakers



.Fan. 26, 1954 RUSSELL 2,666,980

METHOD OF MAKING LOUD-SPEAKERS Original Filed April 2, 1947 2Sheets-Sheet 1 iiiiiii INVENTOR. EARL L. RUSSELL ATTOQNEIS Jan. 26, 1954RUSSELL 2,666,980

METHOD OF MAKING LOUD-SPEAKERS Original Filed April 2, 1947 2Sheets-Sheet 2 INVENTOR. EHRL L. Russem FITToR eYs Patented Jan. 26,1954 2,666,980 METHOD OF MAKING LOUD-SPEAKERS Earl L. Russell,Cleveland, Ohio, assignor to The Rola Company, Inc., Cleveland, Ohio, acorporation of Ohio Original application April 2, 1947, Serial No.

738,894, now Patent No.

2,524,836, dated October 10, 1950. Divided and this application November17, 1949, Serial 1 Claim.

This application is a division of my copending application Serial No.738,894, filed April 2, 1947, now Patent 2,524,836, issued October 10,1950 and relates to permanent magnet loudspeakers and particularly to amethod of making permanent magnet loud speakers of the type disclosed inthe aforesaid application.

Loud speakers utilizing a permanent magnet for the field structure aresubject to the accumulation of foreign particles in the confined spacebetween the voice coil forms and the opening therefor in the front plateof the magnetic structure. Great care must be exercised in themanufacture and assembly of the loud speaker to avoid the possibility ofmagnetic particles being attracted to and held by the magneticstructure, as otherwise their presence would interfere with the normalreciprocating movement of the voice coil Within the air gap and cause ascratching noise in the reproduction. The cen tering of the voice coilform within the air gap is also important. The method of assembly mustbe such that the proper spacing is maintained between the componentparts and at the same time must enable the speaker to withstand roughhandling incident to the packing and shipment of the loud speakers fromthe place of production to the set manufacturer, and then to theultimate user.

An effort heretofore has been made to overcome the aforementioneddifiiculty by permanently fastening the cone and housing assembly to thefield assembly after the voice coil form has been centered by means of agauge with respect to the pole tip of the magnetic structure. Thedifliculty with such assembly, however, has been that if any magneticparticles should be entrapped between the voice coil form and the poletip, or if the voice coil is not centered exactly, it

'has been necessary to destroy the diaphragm,

the spider or centering member, the voice coil and the form in order toget at the space in the region of the air gap for the purpose of freeingthe gap of foreign particles or in order to recenter the voice coil. Inloud speakers utilizing a permanent magnet, such occurrence is apt to besufficiently frequent to constitute a major item in the servicing andrepairing of loud speakers.

An object of the present invention is to provide a method of assemblinga loud speaker wherein the cone or diaphragm and its associated housingassembly can be removed from the field as sembly without destroying ordisturbing the relationship of the parts forming the diaphragm assembly,thereby enabling the field structure,

of a cone to the in the region of the air gap, to be effectively cleanedor centered and the parts reassembled in an expeditious manner.

Referring now to the drawings, Fig. l is a side elevation of a loudspeaker embodying the present invention; Fig. 2 is an exploded view inside elevation of the assembly shown in Fig. 1; Fig. 3 is an end View ofthe field structure as viewed in the direction indicated by the arrows3-3 in Fig. 2; Fig. 4 is a rear view of the assembled loud speaker witha portion thereof broken away; Fig. 5 is a section taken on a planeindicated by the line 55 in Fig. 4, and Fig. 6 is a section taken on aplane indicated by the line 66 in Fig. 4.

The loud speaker with which the present invention is shown has apermanent magnetic field which includes a shell type core, indicated ingeneral at [0, and preferably comprises a strip of metal that is bent toform an open frame having a front plate H, a back plate 12, a top plateI3 and a bottom plate i l. The front plate has an opening l5 therein andthe back plate has a pole piece It extending into the shell andsubstantially parallel to the top and bottom plates thereof. The polepiece terminates in a pole tip H which is concentrically disposed withinthe opening l5 and cooperates therewith to provide the air gap in whichthe voice coil is adapted to operate in the usual way. The pole piece 16is held within central position within the shell by means of a resilientcup-shaped member 20 that is soldered or otherwise securely fixed to theback of the front plate and is adapted to en gage a tapered surface 21on the pole piece to exert tension thereagainst, so as to hold itfilrnlilly in central position with respect to the s e The loud speakerof the-present invention in cludes a diaphragm 25 preferablein the formthroat of which a voice coil form 26 is attached. The form carries theusual voice coil 2! and is held in centered position by a spider orcentering member 30 which extends from the neck of the diaphragm to thespace 3| of the cone housing 32. The periphery of the cone is fastened,as by cement and gasket 33, to the periphery of the housing.

The field structure is attached to the cone assembly by fasteningmembers 35 which extend through openings 36 in a plate 37 and are inthreaded engagement with registering openings in the baseof. the conehousing. As is shown in Fig. 6, theopenings 35 are larger than thediameter of the threaded shank of the fastener 35,

as a result of which adjustment may be made between the field structureand the cone assembly whenever the screws are loosened.

The foregoing described the component parts of the assembly,.but forcarrying .out the assembly, the plate 3'! isgstaked or-iotherwisesecurely fastened to the front plate H, as by bosses 40 which areextruded from the front plate and are adapted to enter correspondinglyshaped openings in the plate 37. Additionally, the attachment is made bythreadedjastenmg.members-4l, as is shown in Fig. 3. The plate. andshellas a unit are then fastened to the cone housing 32 by means of thesecuring members 55, these being accessible from the rear of the housingas is shown in 4, inasmuch-as the plate 311s wider than the material ofwhich the 1shell i0 .is made.

After the shell has been assembled to the housing, then the pole pieceit is centrally located therein by means of asuitable gaugev placedbetween the pole tip and the wall of the opening 15, and is locked inplace by; the resilient center- :ing member 20, after which solder isapplied to hold the pole piece to the back wall of the shell and'to holdthe centering member to theiront plate of theshell.

After the assembly of the magnetic structure,

the. centering member 30 is cement-ed at its outer periphery to the base3| of the cone housing, while being centered with respect to the axisofthe pole tip by means ,of a gauge that is inserted within the air gap.lihe assembly of the cone and its associated-voice coil rorm to thecentering member 30 is made by applying cement to theineck of the cone.on the outer portion thereof and-then inserting the voice coil ,forminto the --air gap, using a customary centering gauge to space ,it withrespect to the pole piece. The .form isinserted until the centeringmember fits snugly against the neck of the cone,whereu pon the cementoperates efiectivelyto join the two parts together. While the centeringgauge is -stillrin position,-the base of the cone is cemented tothevcone housing and sealed by means .of the gasket 33 which is cementedthereto.

In the-event of the voice coil form being inaccurately centered withrespect to the polepiece, then itis only necessary to loosenthe screws.35

and move the field assembly with respectto the ,cone assembly, using thecustomary centering gauge between the voice coil ,form and the .pole

tip, and then tightemng theimembers e5.

Heretofore it has been necessary to destroy the cone, together with itsassociated centering .member, voice coil and voice coil iormin ,order torelocate a form with respect .to the walls of the air gap, or to makethe air gap accessible for cleanirgpurposes. Anadvantage of .the presentinvention, however/is that the adjustment and the component parts, andwithout disturbing the 0 ;clean1ng can .bemade-without destroying anyof6 Moreover, the invention is advantageous in that the cone assembly andfield structure may be quickly adjusted merely by the insertion of acentering gauge between the voice coil form and the pole tip at the timeof tightening of the fastening members, which are readily accessiblefrom xthe-exteriorpart of the unit.

1 claim: In alloud speaker having a permanent magnet shell type fieldstructure with an air gap in one F iace a pole pieceand pole piececentering member,-a cone assembly including a housing, and a diaphragmhaving a voice coil and form at one end with a retaining spider having acentral opening for accommodating the voice coil and form, a platehaving an air gap opening for coupling the-shell and pole piece to thecone assemblyythe plate having a width greater than the air gap race ofthe shell and having oversize holes through portions thereofez-ztendingbeyond the air face of the shell adapted to loosely receivesecuring screws therethrough, the method of assembly comprising,positioning and securing the plateto the air gapface of the shell sothat the air gap opening of'the plate is centered with respect to theair gap of the shell, securing the housing to the plate by means ofscrews extending through the oversize holes in theplate and toward thehousing, centering and securing the pole piece in the shell by means ofthe'pole piece centering member, centering the spider with respect tothe pole piece and securing the outer periphery of the spider to thehousing, centering the voice coil and form of the diaphragm through thecentral opening of the spider in the air gap between'the pole piece andshell, securing the adjacent end of the diaphragm to the spider andsecuring the outer end of the diaphragm to the adjacent portion of thehousing.

EARL L. RUSSELL.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,836,076 Kingsiord ec. 15, 1931 1,859,518 Kingsford May 24,1932 1,856,774 Mayer May 3, 1932 1,886,735 Prldham Nov. 8, 19321,905,702 vI-lardisty Apr. 25, 1933 1,906,196 Fisher ,Apr. 25, 19331,941,476 Jensen Jan. 2,1934 2,020,212 Quam, Nov. '5, 1935 2,174.,355.Sundstrom Sept..26,'1939 2,306,291 .Alons Dec. 22, 1942 2,423,037Marquis June 24, 19937 2,524,836 .Russell -1 Oct. 10,1950

